Re: [CAD_CAM_EDM_DRO] Running a Bridgeport Interact 1 Mk1 on single phase 240v

dgsutton2000 wrote:

>I am thinking of getting an old Bridgeport Interact 1 with a TNC 145
>control because the machine is like new. I want to run it on single
>phase and use the 145 control because it will do want I want for now
>and I'm used to Heidenhein, later on I will be converting it to PC
>control which thanks to other members of this group I know which
>direction to go in however that will still be single phase.
>So for now I want to power the machine from UK single phase 240v. To
>start off I was thinking of powering the main motor with an ABS
>single phase to 3 phase controller which will allow me to also
>inject D/C to spindle stop. This will draw 18A max 7A normal and
>allow me to program soft start to keep big current drains off my
>single phase supply, this I'll use anyway PC or TNC ....unless any
>one can see a problem here?
>

This will work fine, assuming the VFD is the right type for the spindle
motor.
If you have a 240 V single-phase supply, you need to have a spindle motor
that can be wired for 240 V 3-phase.

>I then need to power up the servo and TNC unit. The TNC is no
>problem I'll just fit another small transformer but the servos are
>fed from a big 3KVA transformer that's wired across 2 of the 420v
>phases. What I was hoping to do was get the transformer rewound to
>feed in single phase and output the correct voltages of 180-0-180-
>380 to the chokes and drive boards. But I guess this is not that
>simple because I am dealing with what was supposed to be 2 phases
>that are 120 deg
>

No, that is not correct. As long as it is a single transformer primary,
it has
no idea what the phase relationship to anything else is. If it only has 2
wires connected to the mains, and no neutral, then it is single phase, by
definition. it knows no difference, anymore than an ordinary light bulb
would know if wired across two line terminals of a 3-phase system.

It might be a LOT easier and cheaper to find a large enough autotransformer
or other transformer to produce the 420 V supply the servo drive needs.
If the machine's transformer has several windings, and especially if they
are on the outside of the coil, as is VERY common, then the entire
transformer will have to be torn down to get to the primary.

If you can find what we call a "step-down transformer" to get 3KVA of
240 V single phase from 420 V mains, you can turn this transformer around
and step 240 up to 420. These may be common if the 420 3-phase mains
are commin in shops. (We use 480/240 stepdown transformers here, they
are quite common.)

Jon